Strokes are a leading cause of death and paralysis in the world. A stroke occurs when an artery that carries blood to the brain is blocked (i.e., occluded) or ruptures. The blockage or rupture causes reduced blood flow to portions of the brain which results in portions of the brain becoming starved for oxygen or nutrients. If revascularization (i.e., restored blood flow) does not occur, necrosis of brain cells will result.
Blockages that result in strokes are often caused by a blood clot (i.e., thrombus), fatty deposit (i.e., plaque) or other emboli that becomes lodged within the blood vessel. Total occlusions or partial occlusions (i.e., stenosis) are often the result of diseases of the arterial wall. Arterial atherosclerosis is by far the most common arterial disorder and when complicated by thrombosis or embolism it often is the most frequent cause of cerebral ischemia and infarction, resulting in cerebral stroke. Stroke caused by heart disease is primarily due to embolism by thrombotic material forming on the arterial or ventricular wall or the left heart valves. These thrombi can then detach and embolize into the arterial circulation.
Endarterectomy, angioplasty and carotid stenting are procedures targeted at opening an occluded artery; however, they do not prevent progression of new plaque. Even more so, the above treatment methods only provide a solution to localized problems and do not prevent proximal embolic sources, i.e., embolus occurring at remote sites (heart and ascending aorta) to pass through the reopened stenosis in the carotid and occlude smaller arteries in the brain. This is a substantial problem, inasmuch as about one-third of patients suffering from carotid occlusion also have proximal embolic sources leading to stroke.
Introducing filtering means into blood vessels, in particular into veins, has been known for some time. However, filtering devices known in the art often become clogged and need to be cleaned or replaced. When considering the possible cerebral effects of even fine embolic material occluding an artery supplying blood to the brain, the consequences may be fatal or may cause irreversible brain damage. In light of the short period of time during which brain tissue can survive without blood supply, there is a need for improvement in this field.